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Microplastics transfer from mosquito larvae to adults

New route of contamination could spread plastic pollutants even further. Bill Condie reports.

Macro photography of microbeads – microplastic particles in this case found within consumer facial scrub lotion. The particles measuring only a few micrometers in diameter are too small to be trapped during waste water treatment. Small marine animals ingest the microplastics and pass the pollutant up the food chain. Now we discover, mosquito larvae do too.

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We’ve become sadly familiar with the ease with which microplastic pollutants (MP) can be ingested in by aquatic organisms and passed on up the food chain to entirely different ecosystems.

Fish and shellfish sold for human consumption are routinely contaminated with a range of plastics.

But, for the first time, scientists have found that microplastics can move just as easily through one animal’s different life stages – even if those are spent in different habitats.

In a paper published in Biology Letters, UK researchers show the tiny fragments of plastic can be eaten by mosquito larvae and transferred to into a non-feeding (pupa) life stage and subsequently into the adult terrestrial life stage.

This provides another way for microplastics to travel through the environment – effectively dispersed through the air – putting even more animals and insects at risk of contamination.

“Our results have important implications because any aquatic life stage that is able to consume MPs and transfer them to their terrestrial life stage is a potential vector of MPs onto novel aerial and terrestrial habitats,” the authors write.

“Adults are predated on emergence by many animals including dipteran flies … while resting predominantly by spiders and in flight they are the prey of dragonflies, damselflies, birds, such as swallows and swifts, and bats.”

The scientists tracked the plastics using yellow-green carboxylate-modified polystyrene particles in two sizes – two micrometers and 15 micrometers.

They found that transference was dependent on particle size, with the smaller ones transferring readily into pupae and adult stages, while 15-micrometer MPs transferring in much smaller numbers.

This meant that density reduced through the mosquitoes’ life stages.

The problem could be even more widespread.

“While mosquitoes were used here as a model organism, any freshwater insect that can ingest MPs will likely equally transmit plastics into a terrestrial adult stage,” the study says.